Conventionally, in motor-driven vehicles such as electric vehicles and hybrid vehicles, electric power stored in a secondary battery is supplied to an electric motor through an inverter or the like so that driving force for traveling of the vehicles is output. The secondary battery represented as a lithium-ion battery or the like has an increased temperature due to Joule heat generated by taking in and out electric power during traveling, charging, or the like, but the secondary battery is deteriorated or damaged when the temperature thereof exceeds a predetermined temperature. For this reason, a cooler for allowing the secondary battery to be maintained at the predetermined temperature or less is required.
As the conventional cooler for cooling the secondary battery, a device using a vapor compression type refrigeration cycle device for cooling air blown into a vehicle interior in a vehicle air conditioning system is implemented. In the refrigeration cycle device provided with two evaporators interconnected in parallel in a receiver cycle having a receiver which separates gas and liquid of a refrigerant at an outlet of a condenser, air for the vehicle interior is cooled by one of the evaporators and the secondary battery is cooled by the other of the evaporators.
Meanwhile, in order to cope with lack of a heat source for heating in the electric vehicles and the like, an example of using an accumulator cycle as the refrigeration cycle for the vehicle air conditioning system is increased. The accumulator cycle includes an accumulator which separates gas and liquid of a suction refrigerant of a compressor, unlike the receiver cycle. Even in this case, in order to cool the secondary battery, a structure is considered in which two evaporators interconnected in parallel are provided, air is cooled by one of the evaporators and the secondary battery is cooled by the other of the evaporators.
Here, as control for efficiently operating the refrigeration cycle, superheat control (SH control) to control a degree of superheat (SH) of a refrigerant at an outlet of an evaporator is typically performed in the receiver cycle, and subcool control to control a degree of supercooling (subcool) of a refrigerant at an outlet of a condenser is typically performed in the accumulator cycle.
For this reason, in a case in which two evaporators are provided in parallel at a low-pressure side of the refrigeration cycle and pressure reducers are respectively provided upstream of the two evaporators, the receiver cycle is established even when the SH control is performed at both of the two pressure reducers, but the accumulator cycle dose not balance when the subcool control is performed at both of the two pressure reducers. That is, when one point of a refrigerant temperature state at the outlet of the condenser is controlled by the two independent pressure reducers, the refrigerant temperature state is unmistakably determined. For this reason, the subcool control may not be performed at both of the two pressure reducers in the accumulator cycle.
A refrigeration cycle device disclosed in Patent Document 1 is a device in which, in an accumulator cycle, first and second evaporators are arranged in parallel between a radiator and an accumulator, a first pressure reducer is arranged upstream of the first evaporator in a refrigerant flow direction thereof, and a second pressure reducer is arranged upstream of the second evaporator in a refrigerant flow direction thereof. The first pressure reducer is an electric expansion valve and is controlled such that a refrigerant flowing out of the radiator has a temperature within a predetermined range. In addition, the second pressure reducer is a lower-cost mechanical expansion valve compared to the electric expansion valve and is controlled (controlled in an SH manner) such that a refrigerant flowing out of the second evaporator has a degree of superheat within a predetermined range.